Ok, so, this isn't 100 percent set in stone, but...
Neptune... right.. in this setting.. has a ton of different fluids, but in general it has a solid planet at the center, surrounded by an ammonia ocean where the Grafile live.. then the water ocean around that.

The Chiru people swim in the water ocean, so they have legs so they can walk on the occasional thingy floating on the surface, such as ice. Also they have some homes, after a fashion. It's complicated. Only the males can really do well on surfaces, so they sometimes hold men-only type meetings. They still need to get back into the water before long..

when it comes to swimming, though, the females are obviously better, so there's sort of a balance. The females choose the mates, but the males compete with each other to show off. yeah that's.. like Decapodians. Hrmm. Oh well.

they're metallic and scaly.. with obvious severe sexual dimorphism.. males tend to be greener.. and their size.. females being like 25 feet long and males twice that, and over three times as heavy.

Oh the genitalia are interesting too, as they're the reverse of what we're used to, even though the material still exchanges in the same direction. so, more like gas-siphoning than refueling, so to speak.

umm, they lay 8 eggs at a time.. oh they have.. an electric-sense.. like sharks.. once in a while someone manifests contact-shocking abilities, but other than that special powers tend to be like water-manipulating.. which would obviously be useful..

lifespan is 300 Terran years.

Oh, they're calm and educated.. with some minor technological conveniences.. some weapons.. and they only go to war when there's a damn good reason.